Extend a Line to Another Line in FreeCAD Sketch

Extending an open line to meet another line or boundary in a FreeCAD sketch is a fundamental drafting task that ensures geometry forms closed profiles. This guide explains how to quickly bridge the gap between lines using either the dedicated Sketcher Extend tool or parametric geometric constraints.

Method 1: Using the Extend Edge Tool

FreeCAD includes a dedicated tool designed to project and extend geometry to the nearest intersection.

1. Open your sketch in the Sketcher Workbench.
2. Click the Extend edge tool from the toolbar (located in the same dropdown menu as the Trim edge tool).
3. Hover your cursor near the endpoint of the open line you want to extend. FreeCAD will highlight the line segment and display a preview of the extension toward the nearest boundary.
4. Click once on the line to apply the extension. The line will lengthen until it directly intersects the target line, creating a shared point.

Method 2: Using the Point onto Object Constraint

If you prefer to maintain strict parametric control or if the Extend tool cannot resolve the intersection, you can extend the line using constraints.

1. Click on the open endpoint of the line you wish to extend.
2. Hold down the Ctrl key and click the body of the line you want it to meet.
3. Click the Point onto object constraint icon in the Sketcher toolbar, or press the O key on your keyboard.
4. The endpoint will snap directly onto the target line, automatically extending the line segment to make contact.

Method 3: Joining Endpoints with a Coincident Constraint

If the goal is to join the ends of two lines to form a corner:

1. Click the endpoint of the open line.
2. Hold Ctrl and click the endpoint of the second line.
3. Apply the Coincident constraint (or press the C key). Both endpoints will merge into a single, shared vertex.